This invention relates to a polymetallic supported catalyst component, to a method of preparing the polymetallic supported catalyst component, to the Ziegler-Natta catalyst prepared from the component, to a method of polymerizing at least one alpha-olefin of the formula CH2xe2x95x90CHR where R is H or a C1-12 branched or straight chain alkyl or unsubstituted or substituted cycloalkyl and to the olefin polymers produced using the catalyst.
The polymerization of alpha olefins, particularly propylene, with Ziegler-Natta catalysts, comprising the reaction products of organometallic compounds with transition metal compounds, to produce highly crystalline isotactic polymers is known. Typically the highly crystalline isotactic fraction was separated from the amorphous and low molecular weight and semi-crystalline fractions by extraction with a hydrocarbon solvent, such as hexane or kerosene. Since the advent of these catalysts, research activity in this area has generally been concerned with improving the yield, stereospecificity and morphology of the crystalline isotactic polymers. This was achieved with the development of a highly active and highly stereospecific catalyst system comprising TiCl4 and an electron donor compound (Lewis base) supported on an activated anhydrous MgCl2 solid catalyst component, and an organoaluminum activator as cocatalyst, with or without an electron donor compound. Typically, the propylene homopolymers produced with this catalyst have an isotacticity of greater than 95% as determined by the number fraction of isotactic pentads from 13C NMR analysis and a % XSRT of 2 to 5 wherein the ratio of the I.V. of the XSRT fraction to the I.V. of the whole polymer is less than 0.50. Despite the flexibility of this catalyst system, it does not provide certain soft resins having elastic properties or allow production of an atactic polymer of high molecular weight.
U.S. Pat. No. 4,562,170 describes a supported catalyst component for the polymerization of alpha olefins, particularly ethylene, which requires a metal oxide support material from the metals of Groups 2a, 3a, 4 and 4 of the Periodic Table. The supported component is prepared under anhydrous conditions by the sequential steps of forming a slurry of the metal oxide, preferably dehydrated high surface area silica, adding a solution of an organomagnesium compound, adding and reacting a solution of a hafnium compound, adding and reacting a halogenator, adding and reacting a tetravalent titanium compound and recovering the solid catalyst component. It is used with an organoaluminum cocatalyst in the polymerization of ethylene. A similar catalyst system is described in U.S. Pat. Nos. 4,554,265 and 4,618,660 except that the organomagnesium compound in a solution is first reacted with a zirconium compound in a solution rather than a hafnium compound.
U.S. Pat. Nos. 4,578,373 and 4,665,262 relate to supported catalyst component which is quite similar to those described in U.S. Pat. Nos. 4,562,170, 4,554,265 and 4,618,660 discussed above. The primary difference appears to be that a solution of a zirconium compound, hafnium compound or mixtures thereof is used instead of the solution of a hafnium compound or a solution of a zirconium compound.
U.S. Pat. Nos. 4,310,648 and 4,356,111 disclose an olefin polymerization catalyst component prepared by reacting a trivalent or tetravalent titanium compound, a zirconium compound, and organomagnesium compound and a halogen source, such a ethylaluminum dichloride.
The present invention, in one embodiment, provides a polymetallic supported catalyst component comprising an activated anhydrous MgCl2, or alcohol adduct thereof, solid support which has been treated with at least one treatment of at least two halogen-containing transition metal compounds, wherein one is a halogen-containing titanium metal compound and one is a halogen-containing non-titanium transition metal compound, optionally, in the presence of an electron donor.
Another aspect of this invention is the process for producing the polymetallic supported catalyst component comprising treating the activated anhydrous MgCl2, alcohol adduct thereof or precursor thereof with at least two treatments of at least two halogen-containing transition metal compounds, one of which is a halogen-containing titanium compound and one of which is a halogen-containing non-titanium transition metal compound, sequentially or simultaneously, optionally, in the presence of a polar, substantially inert solvent in which the metal compounds are at least sparingly soluble and the support is substantially insoluble, and optionally in the presence of an electron donor, initially at 0xc2x0 C. and then at a temperature from about 30xc2x0 to about 120xc2x0 C. for a period of time from 30 to 240 minutes for each treatment, with the solids being isolated in between treatments.
In another embodiment of the invention, a catalyst for the polymerization of at least one alpha-olefin of the formula CH2xe2x95x90CHR, where R is H or a C1-12 branched or straight chain alkyl or substituted or unsubstituted cycloalkyl, is provided by reacting the aforementioned supported catalyst component with an organometallic cocatalyst, optionally in the presence of an electron donor. When substituted, the cycloalkyl is preferably substituted in the 4 position. Typical substituent groups are C1-13 alkyl or halide or both.
Another aspect of this invention is the polymerization of at least one alpha-olefin having the above formula with the catalyst of this invention.
In yet another embodiment, this invention provides polymers, especially propylene polymers, which have a controllable atactic content, which is expressed herein in terms of its xylene solubility at room temperature (XSRT), and exhibit a ratio of the IV of the xylene soluble fraction to the IV of the bulk polymer greater than or equal to 0.50.
The activated anhydrous MgCl2 support can be prepared by any of the methods disclosed in U.S. Pat. Nos. 4,544,717, 4,294,721, and 4,220,554, the methods of which are incorporated herein by reference.
Alternatively, the solid catalyst support may be prepared by forming an adduct of magnesium dichloride and an alcohol, such as ethanol, propanol, butanol, isobutanol and 2-ethylhexanol, wherein the molar ratio is 1:1 to 1:3, which then treated further according to this invention.
In another method, a magnesium dichloride/alcohol adduct containing generally 3 moles of alcohol per mole of MgCl2, may be prepared by mixing the alcohol with the magnesium chloride in an inert hydrocarbon liquid immiscible with the adduct, heating the mixture to the fusion temperature of the adduct while stirring vigorously at 2000-5000 rpm using, for example, an Ultra Turrax T-45 N stirrer. The emulsion thus obtained is cooled quickly to cause the adduct to solidify into spherical particles. The adduct particles are dried and partially dealcoholated under an inert atmosphere, such as nitrogen, by gradually increasing the temperature from 50xc2x0 C. to 130xc2x0 C. for a period of time sufficient to reduce the alcohol content from 3 moles to 1-1.5 moles per mole of MgCl2. The resulting partically dealcoholated adduct is in the form of spherical particles having an average diameter of 50 to 350 microns, a surface area, by B.E.T. using a Sorptomatic 1800 apparatus, of about 9 to 50 m2/g and a porosity, as determined with a mercury porosimeter, of 0.6 to 2 cc/g. For example, a MgCl2.3 ROH adduct, where R is a straight or branched C2-10 alkyl, can be prepared according to the ingredients and procedure of example 2 of U.S. Pat. No. 4,399,054, the method of which is incorporated herein by reference, except that the stirring is done at 3,000 rpm instead of 10,000 rpm. The adduct particles thus formed are recovered by filtering, are washed 3 times at room temperature with 500 ml aliquots of anhydrous hexane and gradually heated by increasing the temperature from 50xc2x0 C. to 130xc2x0 C. under nitrogen for a period of time sufficient to reduce the alcohol content from 3 moles to about 1.5 moles per mole of MgCl2.
The activated MgCl2 may be activated prior to the treatment with the halogen-containing transition metal compounds or formed in situ from a precursor of the MgCl2 under conditions which form and activate the magnesium dichloride. One such condition is the reaction of a halogen-containing titanium compound, such as titanium tetrachloride, with a Mg compound, such as Mg(OEt)2, at 30xc2x0 to 120xc2x0 C. with agitation, generally about 250 rpm. The crux is the use of an activated MgCl2, not the means for obtaining same.
The solid catalyst supported component is formed by treating an anhydrous activated MgCl2, an alcohol adduct thereof or an unactivated precursor thereof, in an inert atmosphere, with at least one treatment of at least two halogen-containing transition metal compounds, sequentially or simultaneously or both, wherein one is a halogen-containing titanium compound and one is a halogen-containing non-titanium transition metal compound, optionally, in the presence of a polar liquid medium, initially at 0xc2x0 C. and then at a temperature from 30xc2x0 to 120xc2x0 C. for 30 to 240 minutes, with the solids being isolated in between treatments. The order of treatment with and the relative amounts of the halogen-containing transition metal compounds are used to affect catalyst activity and polymer properties. It is preferred to treat the support with a halogen-containing titanium compound or a combination of a halogen-containing titanium compound and at least one halogen-containing non-titanium transition metal compound first. To obtain a predominantly atactic polymer, i.e., one with a high xylene soluble fraction, it preferred to use a combination of the two compounds in the first treatment. The preferred combination is a halogen-containing titanium compound with a halogen-containing zirconium compound or a halogen-containing hafnium compound. To obtain a predominantly isotactic polymer, i.e. one with a low xylene soluble fraction, it is preferred to treat the support first with a halogen-containing titanium compound in the presence of an electron donor. After the first treatment, the solids are separated and treated one or more times again with various combinations of halogen-containing transition metal compounds with the solids being isolated between treatments.
Any polar liquid medium in which the halogen-containing transition metal compounds are at least sparingly soluble and the solid activated anhydrous MgCl2 support is substantially insoluble, and which is substantially inert with respect to the various components of the supported catalyst component, although it may interact, may be used.
Such solid catalyst component when prepared from anhydrous activated MgCl2 or an unactivated precursor thereof which has been activated show an X-ray spectrum in which the most intense diffraction line which appears in the spectrum of unactivated magnesium dichloride (with a surface area of less than 3 m2/g) is absent, and in its place a broadened halo appears with its maximum intensity shifted with respect to the position of the most intense line of unactivated spectrum, or the most intense diffraction line has a half peak breadth at least 30% greater than that of the most intense diffraction line characteristic of the X-ray spectrum of unactivated magnesium dichloride.
When prepared from a MgCl2. 3 ROH adduct which has been dealcoholated as described above, the solid catalyst component prepared therefrom has an X-ray spectrum where the Mg chloride refections appear, which shows a halo with maximum intensity between angles of 2xe2x8ax96 of 33.5xc2x0 and 35xc2x0, and where the reflection at 2xe2x8ax96 of 14.95xc2x0 is absent. The symbol 2xe2x8ax96=Bragg angle.
Suitable halogen-containing transition metal compounds useful in the preparation of the polymetallic catalyst supported component of this invention include the halides, oxyhalides, alkoxyhalides, hydridohalides and alkylhalides of Sc, Ti, Zr, Hf, V, Nb and Ta. The halide may be chlorine or bromine. The alkoxyhalides and alkylhalides typically have 1-12 carbon atoms and are both straight and branched. The chlorides of Ti, Zr and Hf are preferred.
Scandium trichloride and scandium tribromide are typical scandium compounds useful in the preparation of the supported component of this invention. Scandium trichloride is preferred.
Examples of suitable titanium compounds include titanium tetrachloride, titanium tetrabromide, titanium oxychloride, titanium oxybromide and trichlorotitanium ethoxide. Titanium tetrachloride is preferred.
Suitable zirconium compounds include zirconium tetrachloride, zirconium tetrabromide, zirconyl bromide and zirconyl chloride. Zirconium tetrachloride is preferred.
Typical hafnium compounds include hafnium tetrachloride, hafnium tetrabromide, hafnium oxybromide and hafnium oxychloride. The preferred hafnium compound is hafnium tetrachloride.
Examples of suitable vanadium compounds include vanadium tetrachloride, vanadium tetrabromide, vanadyl chloride and vanadyl bromide. Vanadyl chloride is preferred.
Suitable niobium compounds include niobium pentachloride, niobium pentabromide, niobium oxychloride and niobium oxybromide. The preferred niobium compound is niobium pentachloride.
Typical tantalum compounds useful in the practice of this invention include tantalum pentachloride and tantalum pentabromide. Tantalum pentachloride is preferred.
The quantity of the transition metal compounds used in preparing the solid supported catalyst component of this invention is from 5 to 100 moles per mole of the MgCl2, preferably from 10 to 50 moles, most preferable from 10 to 25 moles. The ratio of Ti metal to the other transition metal or transition metals, as the case may be, is typically from 10:1 to 4000:1, preferably 250:1 to 25:1.
The transition metal compounds can be used neat (undiluted) or in a substantially inert polar liquid medium. A preactivated anhydrous MgCl2, or a Mg compound capable of forming MgCl2 which is then activated when treated with the halogen-containing titanium metal compound, at a temperature from 30xc2x0 to 120xc2x0 C., can be used.
Typically, the reaction ingredients are stirred at about 250 to 300 rpm in a 1 liter vessel. The reaction is generally carried out over a period of time from about 30 to about 240 minutes, preferably from 60 to 180 minutes, most preferably 80 to 100 minutes, per each treatment.
Typical polar liquid mediums useful in the preparation of the supported catalyst component include acetonitrile, methylene chloride, chlorobenzene, 1,2-dichloroethane and mixtures of chloroform and hydrocarbon solvents. Methylene chloride and 1,2-dichloroethane are the preferred polar liquid media. When a mixture of chloroform and hydrocarbon material is used, the suitable hydrocarbon materials include kerosene, n-pentane, isopentane, n-hexane, isohexane and n-heptane. Normal hexane is the preferred hydrocarbon material.
Suitable election donors for use in the preparation of the supported catalyst component of this invention include acid amides, acid anhydrides, ketones, aldehydes and monofunctional and difunctional organic acid esters having from 2 to 15 carbon atoms, such as methyl acetate, ethyl acetate, vinyl acetate, cyclohexyl acetate, ethyl propionate, methyl butyrate, ethyl valerate, methyl benzoate, ethylbenzoate, butyl benzoate, phenyl benzoate, methyl toluate, ethyl toluate, amyl toluate, methyl anisate, ethylethoxybenzoate, ethyl pivalate, ethyl naphthoate, dimethyl phthalate, diethyl phthalate and diisobutyl phthalate (DIBP). In addition, 1,3- and 1,4- and 1,5- and greater diethers, which may be substituted on all carbons, and, preferably, have substitutions on at least one of the internal carbons may be used. Suitable diethers include 2,2-diisobutyl-1,3-dimethoxypropane, 2-isopropyl-2-isopentyl-1,3-dimethoxypropane, 2,2-bis(cyclohexylmethyl)-1,3-dimethoxypropane, 2,3-diphenyl-1,4-diethoxybutane, 2,3-dicyclohexyl-1,4-diethoxybutane, 2,3-dicyclohexyl-1,4-dimethoxybutane, 2,3-bis(p-fluorophenyl)-1,4-dimethoxy-butane, 2,4-diphenyl-1,5-dimethoxypentane, and 2,4-diisopropyl-1,5-dimethoxypentane. Difunctional esters, such as diisobutyl phthalate are preferred.
The supported catalyst component prepared according to this invention is recovered and washed with several, e.g. approx. 5-20, aliquots of a substantially inert solvent. Suitable solvents for washing the catalyst component include methylene chloride, 1,2-dichloroethane, hexane and chloroform/hexane mixtures wherein the amount of chloroform can be from 10% to 75% of the mixture.
The catalyst component may be stored dry or as a slurry in a suitable nonreactive atomosphere, i.e., under an inert atmosphere without exposure to heat or light, either artificial or natural, for at least 6 months up to several years.
Organometallic compounds suitable for use in the preparation of the catalyst of this invention include organoaluminum compounds, organogallium compounds, organotransition metal compounds, organomagnesium compounds and organozinc compounds. In general, alkylaluminum compounds are preferred.
Triisobutylaluminum (TIBAL), diisobutylaluminum hydride (DIBAL-H), diisobutylaluminum ethoxide, triethylgallium, triethyl aluminum (TEAL), triisopropylaluminum, diisobutyl zinc, diethylzinc, dialkyl magnesium, such as dimethylmagnesium and diethylmagnesium, and compounds containing two or more Al atoms linked to each other through hetero-atoms, such as:
(C2H5)2Alxe2x80x94Oxe2x80x94Al(C2H5)2;

are typical metal alkyl compounds. Generally from about 5 to about 20 mmoles of organometallic activator per 0.005 to 0.05 g of supported catalyst component is used.
Suitable electron donors for use with the organometallic compounds are organosilane compounds having silicon (IV) as the central atom with at least two alkoxy groups bonded thereto and a xe2x80x94OCOR, xe2x80x94NR2 or xe2x80x94R group or two of these groups which may be the same or different bonded thereto, where R is an alkyl, alkenyl, aryl, arylalkyl or cycloalkyl with 1-20 carbon atoms. Such compounds are described in U.S. Pat. Nos. 4,472,524, 4,522,930, 4,560,671, 4,581,342 and 4,657,882. In addition, organosilane compounds containing a Sixe2x80x94N bond, wherein the nitrogen is part of a 5-8 membered heterocyclic ring can be used. Examples of such organosilane compounds are diphenyldimethoxysilane (DPMS), dimesityldimethoxysilane (DMMS), t-butyl(4-methyl)piperidyldimethoxysilane (TB4MS), t-butyl(2-methyl)piperidyldimethoxysilane, isobutyl(4-methyl)piperidyldimethoxysilane, dicyclohexyldimethoxysilane, t-butyltriethoxysilane and cyclohexyltriethoxysilane. Dimesityldimethoxysilane and t-butyl-(4-methyl)piperidyldimethoxysilane are preferred. A method of preparing TB4MS is disclosed in U.S. Ser. No. 386,183, filed Jul. 26, 1989 and the disclosure of this method is incorporated herein by reference. The remaining silanes are commercially available.
In the catalysts of this invention the ratio of Mg:Me is from about 0.9 to about 25.0, the ratio of Mxe2x80x2:Ti is from about 0.1 to 25.0, the ratio of Al:Me is about 20 to about 40,000. Me is Ti, Sc, Zr, Hf, V, Nb, Ta or combinations thereof. Mxe2x80x2 is Sc, Zr, Hf, V, Nb, Ta or combinations thereof.
Alpha olefins which can be polymerized by the catalyst of this invention include ethylene, propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene, vinyl cyclohexane, allyl benzene, allyl cyclohexane, vinyl cyclopentane or mixtures thereof.
The polymerization reactions using the catalyst of this invention are carried out in an inert atmosphere in the presence of liquid or gaseous monomer or combinations thereof and, optionally, in the presence of an inert hydrocarbon solvent, at a temperature from about 30xc2x0 to about 100xc2x0 C., preferably from 50xc2x0 to 80xc2x0 C., and at a pressure from about atmospheric to about 1000 psi, preferably from about 200 to 500 psi in liquid phase polymerization and from atmospheric to about 600 psi in gas phase polymerization. Typical residence times are from about 15 minutes to about 6 hours, preferably from 1 to 4 hours.
The catalyst system, i.e., the polymetallic supported component, the organometallic activator and the electron donor, when used, can be added to the polymerization reactor by separate means substantially simultaneously, regardless of whether the monomer is already in the reactor, or sequentially if the monomer is added to the polymerization reactor later. It is preferred to premix the supported catalyst component and the activator prior to the polymerization for from 3 minutes to about 10 minutes at ambient temperature.
The olefin monomer can be added prior to, with or after the addition of the catalyst system to the polymerization reactor. It is preferred to add it after the addition of the catalyst system.
Hydrogen can be added as needed as a chain transfer agent for reduction in the molecular weight of the polymer.
The polymerization reactions can be done in slurry, liquid or gas phase processes, or in a combination of liquid and gas phase processes using separate reactors, all of which can be done either by batch or continuously.
The catalysts may be precontacted with small quantities of olefin monomer (prepolymerization), maintaining the catalyst in suspension in a hydrocarbon solvent and polymerizing at a temperature of 60xc2x0 C. or below for a time sufficient to produce a quantity of polymer from 0.5 to 3 times the weight of the catalyst.
This prepolymerization also can be done in liquid or gaseous monomer to produce, in this case, a quantity of polymer up to 1000 times the catalyst weight.
Unless otherwise specified, the following analytical methods were used to characterize the supported catalyst component samples and the polymer samples.
The concentration of active metals in the supported catalyst components were determined by atomic absorption spectrophotometry using a Perkin Elmer Model 3030. To analyze for Mg, Ti, Sc and V, the samples (0.07 gxc2x10.01) were hydrolyzed with 25 ml of 2N H2SO4 solution containing 0.2% KCl by weight, in a sealed container under an inert gas. The samples were filtered, and aliquots were diluted as necessary based on metal concentration. The resultant aliquots were analyzed by flame AA using standard techniques as described in xe2x80x9cAnalytical Methods for Atomic Absorption Spectrophotometryxe2x80x9d, Perkin-Elmer Corp., Norwalk, Conn. The same procedure was used for Zr and Hf except that a 1% HF solution containing 0.2 wt % Al (added as AlCl3.6 H2O) was used instead of the 2N H2SO4 solution.
The organic compounds in the supported catalyst component were determined by gas chromatography. The sample (0.5-1.0 g) was dissolved in 20 ml acetone and 10 ml of an internal standard solution of 0.058 to 0.060 molar n-dodecane in acetone was added. When the supported catalyst component contained an electron donor, di(n-butyl)phthalate was added to the internal standard solution in an amount such that a 0.035 to 0.037 molar di(n-butyl)phthalate solution is formed. Then 15% NH4OH was added dropwise until the solution was at pH 7 to precipitate the metals which were removed by filtration. The filtrate was analyzed by gas chromatography, using a HP-5880 gas chromatograph with FID (flame ionization detector). The column is a 0.530 mm ID fused silica wide-bore capillary column coated with Supelcowax 10.
The intrinsic viscosity of the resultant polymers was determined in decalin at 135xc2x0 C. using a Ubbelohde type viscometer tube by the method of J. H. Elliott et al., J. Applied Polymer Sci. 14, 2947-2963 (1970).
The % xylene soluble fraction was determined by dissolving a 2 g sample in 200 ml xylene at 135xc2x0 C., cooling in a constant temperature bath to 22xc2x0 C. and filtering through fast filter paper. An aliquot of the filtrate was evaporated to dryness, the residue weighed and the weight % soluble fraction calculated.
The melting point and heat of fusion were determined by differential scanning calorimetry (DSC) using a DuPont 9900 controller with a DuPont 910 DSC cell. Melting data was obtained under a nitrogen atmosphere at a 20xc2x0/minute heating rate after quenching from the melt.
A Nicolet 360 spectrometer was used to determine the atactic, syndiotactic and isotactic content based on 13C NMR pentad sequence analysis (of methyl resonances) described in J. C. Randall, xe2x80x9cPolymer Sequence Determinationxe2x80x9d Academic Press, N.Y. (1977).
Tensile strength was determined according to the procedures of ASTM D412.
A Nicolet 740 SX FT-infrared spectrophotometer was used to quantify the monomers in copolymer samples.
The following examples illustrate the specific embodiments of the instant invention.
In the examples, dry and oxygen-free solvents were used. The solvents were dried by storing over activated molecular sieves or by distillation from CaH2. The transition metal compounds were used as received from the manufacturer. The electron donors were dried over activated 4A molecular sieves, neat or as solutions in hexane, prior to use. All preparations of the solid supported catalyst component and polymerization reactions were carried out under an inert atmosphere.
All percentages are by weight unless otherwise indicated. Ambient or room temperature is approximately 25xc2x0 C.